Scalable cavity quantum electrodynamics

Single photons are ideal carriers of quantum information but typically interact weakly with each

other. To exploit the effective photon-photon interactions that lie at the heart of many quantum

information applications, strong optical nonlinearities are required. In this project, which is aligned

with a £6m EPSRC Programme Grant, you will develop and study semiconductor quantum systems

that provide scalable, deterministic nonlinear interactions down to the single photon level; an

essential requirement for optical quantum network elements such as single-photon switches, logic

gates and repeaters.

The project will push the boundaries of on-chip, semiconductor cavity-quantum dot (QD) systems,

ready for exploitation in quantum information applications, by moving into the extreme quantum

regime in tunable cavity structures. You will develop QD-cavity systems operating in this extreme

quantum regime where strong coupling leads to hybridisation of photons with QD excitons to form

polaritons. The associated ladder of quantized energy levels that scales in energy nonlinearly as the

polariton number increases will be harnessed to produce a scalable, on-chip source of selectable

photon number states. Scale-up will involve producing a 1D array of tunable, coupled QD-cavities to

detect optical signatures of quantum phase transitions and entanglement, opening up new frontiers

in on-chip quantum many body physics. Through control of system dissipation and driving you will

be able to explore long-range, steady state entanglement and indefinitely long-lived photon-

localised (self-trapped) steady-states for important application in quantum networks.